1. Field of the Invention
The present invention relates to methods of and systems for providing position information representing the current position of a portable communications device such as a mobile or portable telephone for the person carrying another portable telephone or a similar communications terminal device.
2. Description of the Related Art
Portable telephones are already known which have a position measuring function such as the function of the GPS (Global Positioning System) which is in actual use in car navigation systems. Services are available in recent years for providing such position information representing the current position of a portable telephone for the person carrying another portable telephone.
FIGS. 20 and 21 show two systems for providing position information which utilize the above position information providing service.
With the system shown in FIG. 20, both a portable telephone E and a portable telephone F can be connected to a position information service center 6 via a base station (not shown).
The portable telephone E has a GPS position measuring function. The telephone E receives GPS position data transmitted from a GPS satellite 4 and prepares position information comprising the latitude and longitude of its own position based on the received position data. The position data prepared is supplied via the base station to the service center 6, where the position information is stored in a database 60 along with information for identifying the telephone E.
When an information request signal requesting to provide information about the position of the telephone E is fed from the telephone F to the service center 6 via the base station, the service center 6 checks whether the password contained in the request signal matches the password of the telephone E. If a match is found, the position information as to the telephone E is supplied from the service center 6 to the telephone F via the base station. In this way, the person carrying the telephone F can recognize the current position of the person carrying the telephone E only when the former knows the password of the telephone E.
With the position information providing system shown in FIG. 21, on the other hand, both portable telephone G and portable telephone H can be connected to a position information service center 7 via a base station (not shown).
The portable telephone G, which has a GPS position measuring function, receives GPS position data from the GPS satellite 4 and prepares position information comprising the latitude and longitude of its own position based on the position data received. The position information prepared is stored in a memory incorporated in the telephone G.
When an information request signal requesting to provide information about the position of the telephone G is fed from the telephone H to the service center 7 via the base station, the service center 7 supplies a signal demanding transmission of the position information to the telephone G. The telephone G checks whether the password contained in the transmission demand signal matches the password of its own. If a match is found, the position information as to the telephone G is supplied from the telephone G to the telephone H via the base station and the service center 7. In this way, the person carrying the telephone H can recognize the current position of the person carrying the telephone G only when the former knows the password of the telephone G.
With the two position information providing systems described, the information as to the position of a portable telephone is provided only for one who knows the password of the telephone, whereby the privacy of the one possessing the telephone is protected.
Although there is a time zone during which the person carrying a portable telephone does not like to have her or his own current position known even by those to whom he has told his own password, the two conventional position information providing systems enable those who know the password to recognize the current position of the person at all times if they request the service center to provide the position information. The systems therefore have the problem of failing to reliably protect the privacy of the person possessing the telephone.